The motor is generally driven at a constant speed, whereby the vertical speed of the needle head as a consequence of the function of the crank-drive is sinusoidal, so that the pickle distribution in the meat product due to the varying speed of the needle head will also vary, the needles having varying retention time in the various meat layers, whereby meat areas in which the needles have a high speed will receive a smaller amount of pickle than meat areas in which the needles have a lower speed.
In order to remedy this problem it has been suggested to utilize mechanical curve path systems, partly capable of compensating for the sinusoidal speed variation of the crank throw and thus providing the needle head with an almost constant speed in the injection area. Such systems do, however, have the disadvantage that they are rapidly worn and costly to manufacture and maintain, and also are noisy.